Automatic transmissions have been used in various types of vehicles for a fairly long period of time. As is known, such automatic transmissions have favored the operation of a starting clutch and a clutch coupling, as well as the assortments of switch valves and the engagement and the disengagement of gears is made possible with the help of hydraulic actuators which were developed as piston-cylinder arrangements. On the other hand, there are vehicles in existence that only rely upon a starting clutch or a clutch coupling or on those elements of the transmission that are purely essential. Activation of the aforementioned actuator is controlled by the transmission gearbox with the aid of control and regulating programs, based on information about the driving situation, the shifting situation as well as the desired performance of the vehicle operator in relation to the clutch and the shift options.
Even if these transmissions, compared to other types of automatic transmissions such as continuous variable transmissions or conventional stepped automatic transmissions using planetary gears, are simple in construction and relatively inexpensive, these automatic gearboxes exhibit an interruption in traction during shifting operations, which the operator or passengers of the vehicles in particular can experience as uncomfortable. The interruption of traction with the use of these types of automatic transmissions in commercial vehicles, however, can also prove to be disadvantageous or at least as having a diminished comfort when, for example, a truck with a heavy load at an intersection can only execute a very slow starting process.
Those skilled in the art know that a gear ratio change sequence in an automatic transmission can be roughly subdivided into three phases. For a motor vehicle proceeding in a driving state, first there is the gear disconnection of the gear step previously utilized, as well as disengagement of the starting clutch and the clutch coupling, through which the torque transfer from the motor to the transmission is interrupted. Following this is the selection of the new gear position for shifting and, as the case may be, engagement of the necessary transmission elements for the new transmission gear after which the coupling is engaged and a new load build up follows.
For all of these shifting phases, the torque of the vehicle is influence deviated from the real wishes of the driver, who obviously wishes a forward creep free of any tractive force interruption. The primary goal of a person skilled in the art of the development of transmissions is, therefore, to attain as quickly as possible the necessary shifting intervals for each of these phases. In contrast, a very short shifting causes a diminution of the shifting comfort as well as stronger mechanical stress on the transmission components involved in the shifting process through an associated rapid change in torque. For these mentioned reasons, the actually realized shifting time in an automatic transmission is always a compromise between conflicting interests relevant to the shortest possible shifting time, the highest possible shifting comfort as well as the lowest possible component stresses.
The invention is based upon the knowledge that a portion of the factors influencing actual shifting time are not constant but rather are a function of the respective driving situation, the individual motor vehicle configuration for a specified vehicle type, as well as different driving preferences regarding the comfort and the speed of shifting.
Purely theoretically, a number of combinations to be applied arise from the variables influencing the optimal shifting sequence which can no longer be meaningfully controlled by a control and regulatory program in this regard, which would ultimately lead to many different shifting operations with individual shifting times, component loads and shifting comfort.
Moreover, a desire exists on the part of manufacturers of automated transmissions from the point of view of cost-savings of developing a uniform control and regulation program for all these types of transmissions which takes into consideration the respective motor vehicle type, its manner of use, as well as the individual driving conditions and the driving preferences.
Against this background, the invention is based upon the objective of presenting a method for controlling an automatic transmission with which, as a function of the mentioned influencing factors, such as possibly the driving conditions, the vehicle configuration and the performance wish of the operator, where a shifting operation which is appropriate to the situation and optimal with regards to its duration, shifting comfort and the individual component stresses can be implemented with an automatic transmission. Moreover, this method should be suited for being used without major changes in the transmission gearbox for various types of automatic gearboxes.